Machsupport Forum
Tangent Corner => Tangent Corner => Topic started by: Jimster on January 15, 2014, 10:00:38 AM
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Some really blonde questions coming. I'm thinking of having a go at cutting threads on my mach3 converted Bridgeport interact. Is it possible to use a normal threading (hand type) tap or do I have to use a thread mill? Assuming I can use a normal tap, can I use a std m10x 1.5mm tap to create an thread of m20x1.5mm?
Thanks
Jim
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It is better to use a single point tool like a lathe threading bar, you can then use the wizards to create the g-code
http://www.shop-apt.co.uk/snr-internal-threading-bars-apt/snr-0010-k11-internal-threading-bar.html
http://www.shop-apt.co.uk/metric-iso-internal-threading-inserts/11nr-150-iso-t300-threading-inserts-internal.html
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That's good news, they are a LOT cheaper than the thread mills I saw for over £150 (which gave me a nose bleed) I've got some of those from my lathe, I suppose I'd better pull my finger out and fit the VFD and spindle encoder.
Thanks for the info
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You don't need a VFD or spindle encoder to do thread milling with a single point tool. On a lathe you need an encoder. Thread milling is done with a spiral tool path. Typically you want to spiral upwards from the bottom of the hole, because you are climbing out of the chips instead diving into them.
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Thanks for the extra info, that's good to know. So I only need the VFD and spindle encoder for using regular taps?
I assume I could cut internal and external threads with the tool posted by Graham above?
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Yes regular taps need the Z axis synchronized with the spindle. Thread milling is just a spiral milling operation, X, Y and Z are synchronized already.
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Yes you can do internal and external threads with the same tool, but it has to fit into the hole for internal threads. Thread milling is great for tapered pipe threads because the diameters are large relative to the thread length and it takes huge torque to use a tap and die on a pipe thread.
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I want me make a cam cover for my engine, I need to make a thread for the oil filler cap, about 50mm diameter, so this will be perfect
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Yep,
You can make any pitch, inside or outside in nearly any diameter with just one tool, like a lathe. It is slower than tapping in the small sizes most of the time, but comes into it's own on parts like what you are making where even if you could afford the tap you'd probably have no way to turn it!
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What's the difference between and internal and external insert?
Could I use and internal insert to cut an external thread?
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I would say that the internal insert has greater relief. On the outside of a part the surface curves away from the insert. In a hole the surface curves towards the tool so it could rub if you don't have enough relief. I would guess that an internal insert might work okay for occasional outside threading. Certainly worth a try I would think. If I only had a couple of threads to do that is what I would do.
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They are also different "hands" (L/H and R/H) , especially on a lathe.
Graham
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Yes, you are right they very well could be. I thinking in milling terms.